Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/49—Phosphorus-containing compounds
  • C08K5/5399—Phosphorus bound to nitrogen

Definitions

• vulcanized elastomers based on vinylidene fluoride copolymers are well known and are widely employed in a plurality of applicative fields where an exceptional chemical resistance to solvents, lubricants, fuels, acids and the like, even at very high temperatures, is required.
• vulcanizing agents of polynucleofilic compounds and in particular of aromatic polyhydroxyl compounds (or of similar thioderivatives), either as such or in the salified form.
• Another object is that of providing a process for vulcanizing compositions based on vinylidene fluoride elastomeric copolymers, which is free from the shortcomings cited hereinabove and is capable of providing vulcanized articles exhibiting a high adhesion to metal substrates.
• a third object is also that of providing vulcanized compositions based on vinylidene fluoride elastomeric copolymers, free from the drawbacks mentioned in the foregoing, and which may be shaped by injection molding.
• compositions comprising:
• fluorinated or chlorofluorinated ethylenically unsaturated monomers such as e.g. 1-hydropentafluoropropene; 2-hydropentafluoropropene; 1,1-dihydrotetrafluoropropene, partially or thoroughly fluorinated alkyl- and arylvinylethers, and the like;
• an inorganic acid acceptor consisting of one or more basic oxides of divalent metals, selected from the group comprising magnesium oxide, calcium oxide, lead monoxide, zinc oxide and/or of one or more basic lead phosphites, optionally in the form of cationic complexes or chelates;
• A is an arylene radical, n is an integer equal to or higher than 2, B is oxygen or sulphur; C is hydrogen or an alkaline metal, R is an alkylene or cycloalkylene, mono- or polyalkylenecycloalkyl, or alkylenediaryl or oxoalkylenediaryl radical;
• the vulcanizable compositions of the type specified hereinabove are vulcanized by means of a process, which too is an object of the present invention, that consists in first heating said compositions, under pressure, to temperatures in the range from 130° C. to 230° C., preferably from 160° C. to 200° C., during a time from 0.5 to 60 and preferably from 1 to 20 minutes; the articles so obtained are successively postvulcanized in an oven or a furnace, at atmospheric pressure, at temperature ranging from 130° C. to 315° C., preferably from 200° C. to 275° C., for a period of time from 5 to 48 and preferably from 10 to 24 hours.
• the vulcanizable compositions according to this invention can be transformed into articles of any shape and size by extrusion molding and subsequent vulcanization, employing also highly automatized injection technologies; in fact, at the high temperatures which are usual for the injection molding process, no drawbacks occur due to scorching or hot tearing phenomena.
• Such articles exhibit an excellent resistance to permanent set and to compression, a minimum tendency to scorching as a function of the storing time and temperature or of the temperatures of particular processing technologies, such as for example the extrusion, and also a high resistance to thermal ageing; furthermore, they can be bonded to metal substrates of different types, to which they exhibit a considerable adhesion even at high temperatures.
• the process according to the present invention is particularly suitable in the case of copolymers containing from 30 to 70% by moles of vinylidene fluoride and from 70 to 30% by moles of 1-hydropentafluoroprene and/or hexafluoropropene, or in the case of vinylidene fluoride/tetrafluoroethylene/hexafluoropropene and/or 1-hydropentafluoropropene terpolymers, in which the percent amounts of the three monomers respectively range from 40 to 80, from 30 to 10 and from 30 to 10% by moles.
• the process according to the present invention is advantageously utilizable for all the fluorinated polymeric materials of the elastomeric type, optionally containing substituents other than fluorine and chlorine, and also for the mixtures of two or more fluorinated elastomers.
• Preferred compounds to be used according to the present invention as vulcanization accelerators are:
• this compound is prepared from equimolar amounts of A 1 and of sodium tetrafluoroborate in aqueous solution.
• the product precipitates in the form of very fine white crystals having a melting point of 233° C.;
• a 6 [(C 6 H 5 ) 3 P] 2 NB(C 6 H 5 ) 4
• the accelerator amount to be employed in the process according to the present invention depends on whether or not steric hindrances are present in the additive, on the basicity degree of the vulcanizable composition and on many other factors connected with the other particular additives utilized, on the type, shape and dimensions of the article to be manufactured, on the vulcanization conditions and on the heating system and modalities during vulcanization.
• the vulcanizable compositions according to the present invention may contain, in addition to the substances indicated hereinbefore from (I) through (V), carbon black, white and coloured fillers, plasticizers and lubricants already known, such as stearates, arylphosphates, polyethers, polyesters, polyethylene and other known additives, according to the techniques usually employed by the fluorinated elastomers users.
• the components of the vulcanizable compositions of the present invention are easy to incorporate into the vinylidene fluoride elastomeric copolymer, both separately and premixed, or they may be solubilized in solvents and then caused to be adsorbed on inert fillers having a large surface area, without giving rise to any undesired accompanying phenomenon, such as surface efflorescence, caused by migration phenomena inside the vulcanizable composition, due to the high compatibility with the elastomer.
• Another advantage according to the present invention consists in the complete elimination of the undesired "back rinding" phenomena during vulcanization in closed mold and under pressure of articles prepared from fluorinated elastomers, particularly in the case of O-ring gaskets.
• the mixture of bis(triarylphosphin)-iminium salt (0.1-2 parts by weight) and of vulcanizing agent (1-6 parts by weight) is additioned in the fluorinated elastomer (100 parts by weight), before adding the acid acceptor (2-10 parts by weight), with the basic compounds (1-7 parts by weight), the reinforcing and inert fillers, the lubricants, the plasticizers and other optional additives.
• the fluorinated elastomers obtained from the compositions of the present invention are utilizable as sealing gaskets, in both static and dynamic conditions, in the motorized, mechanical, naval fields, as protective garments for the contact with aggressive chemical agents, as sheaths which protect electrical cables when exposed to an intense thermal radiation, and in other similar appliances.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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Cited By (11)

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Citations (3)

• 1983
  • 1983-03-22 IT IT20196/83A patent/IT1163158B/it active
• 1984
  • 1984-03-21 DE DE8484103126T patent/DE3466005D1/de not_active Expired
  • 1984-03-21 EP EP84103126A patent/EP0120462B1/en not_active Expired
  • 1984-03-21 US US06/591,994 patent/US4501858A/en not_active Expired - Fee Related

Patent Citations (3)

Non-Patent Citations (4)

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